“What is the best food to eat when your blood sugar is low?”

Something that has a small amount of simple sugars, some complex carbohydrates, some protein, and some fat. A granola bar is good. So is half a sandwich (either meat or cheese) with a glass of juice.

Simple carbohydrates that provide rapid absorption.

Fruits and non-starchy vegetables. Fruit will be quick, vegetables will last.

I am going to presume from your question that it is non-diabetic. You should 1sr see a Dr. since this type of hypog. can be due to an insulin secreting tumor of the pancreas. Removal of the tumor will cure the problem. If not a tumor, then treatment is food or drink. Rapid acting foods include juices such as orange or grape juice. Other high sugar foods are raisins, ice cream, honey, plain table sugar, grapes, dried fruit, etc. You can also buy glucose tablets over the counter & eat 2 or 3 of those. DON'T over do it. We are tempted to eat too much when we are low. This will push the blood sugar too high and cause the pancreas to put out a lot of insulin to bring it down & produce hypo again-like a roller-coaster. If you have diabetes the bet treatment for hypo is IV glucose or IV or IM glucagon followed by high sugar foods with some protein. At diabetic camp we have had good success with a mixture of peanuts & raisins.

Hypoglycemia (low blood sugars) and foods to eat.
Hypoglycemia is a metabolic state where blood sugars are below normal range. It is usually defined as blood sugar less than 70 mg/dl. The average fasting blood sugars are 70-100mg/dl. Fasting blood sugars above 100mg/dl is abnormal with people without the history of diabetes. Low blood sugars is defined as hypoglyceia, while high blood sugar is a sign of some form of diabetes. Both forms of blood sugars extremes have short term and long term consequences.
The symptoms of low blood sugars are primarily due to the hormones invoved in correcting the low blood sugar. Adrenalin cuases most of the symptoms of the early signs and symptoms of hypoglycemia. Other hormones involved in the correction of the low blood sugars are glucagon, cortisol and growth hormone. Glucagon is involved in the immediate release of sugars from the glucose storages (mainly the liver).
The symptoms of low blood sugars are mainly adrenergic (neurogenic) symptom. Nueroglycopenic symptoms may also occur in sever or prolonged hypoglycemia when the brain lack glucose.
1. Adrenergic (neurogenic or sympathoadrenal activation) symptoms result from activation of the adrenergic (sympathetic) nervous system, primarily mediated by adrenalin.
Adrenergic symptoms include:
-Shakiness
-Nervous or anxious
-Sweating
-Clamminess
-Irritability
-Impatience
-Palpitation
-Confusion
-Lightheaded
-Dizzyiness
-Hunger
-Nausea
-Fatigue
-Skin pallor
2. Nueroglycopenic symptomes are secondary to shotage of sugar in the brain due to hypoglycemia.
-Abnormal mentation
-poor judgement
-Irritability/rage
-Crying
-Emotional lability
-Slurred speech
-Stuper/loss of consciousness
-Siezures
-Coma
-Death
Hypoglycemia or low blood sugars have various causes. Theses causes include:
A. In diabetic patients;
Both type 1 and type 2 diabetic patients may experience symptoms of low blood sugars. Type 2 diabetetic patients can experience syptoms os low blood sugars is they are on medications primarily oral hypoglycemic agens such as glipizide and glyburide. This may happen when the dose of insulin is too much or they are not eating enough carbohydrates to mactch the amount of insulin taken.
In type 1 diabetes low blood sugars are either due to excess insulin, eating less than usual amount of food or skipped meals or exercising more than usual.
B. In none diabetic patients
1. Medications. Taking blood sugar lowering medications that are intended for a diabetic patient (sulfonylurease). There are also medications intended for a different condition but who have side effects of hypoglycemia. These medications may include medications for blood pressure, malaria etc.
3. Illnesses. These include;
-Adrenal insufficiency
-Celiac disease
-Liver disease
-Kidney disease
4. Ketotic hypoglycemia; This condition ocurs;
-In some skinny people who have less glycogen reserve
-During prolonged starvation
-Eating disorder (anorexia nervosa)
-Valley dancers
-Gymnasts
-People exercising excessively
5. Hormone deficiencies.
-Adrenal insuficiency
-Pituitary hormone deficiency (growth hormone or cortisol deficiency)
6.Hypoglycemia due to Reactive Hypoglycemia (post prandial hypoglycemia);
-This hypoglycemia occurs several hours after eating a meal due more insulin production than the body needed.
-In dumping syndrome
7. Hypoglycemia due to metabolic diorders; many metabolic disorderes such as;
-Glycogen storage diseases
-Fatty acid oxidation disorder
-Aminoacid disorders (amino acidopathies)
8. Hypoglycemia due to Insulin overproduction. This could be due to;
-Insulin producing tumors known as insulinomas (mostly in adults)
-Genetic defects in the pancreatic Beta cell potassium channels, calcium chanels, and others (mostly start in infancy)
-Enlarged beta cells of the pancreas known as nesidioblastosis (mostly in babies).
Low blood sugars secondary to insulin should follow a syndrome called whipple triad which consists of symptoms of low blood sugars, low blood sugars at the time of the symptom and improvement of the symptoms with the correction of low blood sugars.
Consequencies of hypoglycemia; Hypoglycemia of any cause should never be taken lightly. Blood sugars should be kept >70mg/dl at all times.Our brain depends primarily on normal glucose level. In the absence of normal glucose the brain will suffer more than any tissue in the human body. Early recognition of the signs and symptoms of low blood sugar and prompt treament is vital to preventing life threatening injuries.If hypoglycemia is not recognized and treated early and proptly, it can lead to seizures, falls, injuries, accidents and even death.
Causes of hypoglycemia should be investigated properly and be treated promptly. Proper measures should be taken to prevent the ocurrence of hypoglycemia if the cause can not be fixed.
Going back to to you: You are experiencing low blood sugars. You are probably experiencing the full range of the signs and symptoms of hypoglycemia. There are many causes of low blood sugars.
If you have diabetes and you are on either oral anti-diabetes medications or on some form of insulin regimen, the medications should be adjusted or the amount of food consumed should match the amount of insulin taken at each meal. If you are excerscing excessively, insulin should be lowere appropraitely or apropraite amount of food should be consumed to prevent the occurence of hypoglycemia.
If you have no diabetes, the causes of hypoglycemia should be investigated thoroughly. Once the cause/causes are identified treatment plan should be hammered out. The best option in preventing hypoglycemia should be eliminating the cause of the hypoglycemia completely. If eliminating the cause is not possible, reasonable treatment plan should be worked out to keep the blood sugars >70mg/dl at all times to prevent acute and chronic complications of hypoglycemia.
If you are experiencing the signs and syptoms of low blood sugar, the first step is to check your blood sugars (using home self monitoring blood glucose machine) to make sure you really have low blood sugars and not other medical or hormonal conditions. If the syptoms are due to low blood sugars you should take sugar drinks to keep the blood sugars >70mg/dl at all time using fast acting sugars such as juice or milk. You should seek help from your primary care doctor first. He/She will perform proper evaluation and will determine if you need to see an endocrinologist for further evaluation and treatment of the hypoglycemia.
If you keep on experiencing the signs and syptoms of hypoglycemia, whether you truly have low blood sugars or other medical problems, you need proper and prompt evaluation by your primary care doctor who will determine the next appropraite steps. Ignoring signs and symptoms of low blood sugars with or without the actual low blood sugar will be a mistake.
The foods that are helpful in managing low blood sugars depend on what the level of the blood sugars are. If your blood sugar is 70-80 mg/d you may take crackers and peanut butter or any form of starch which will gradually raise your blood sugar.
if your blood sugar If your blood sugar is 55-70 mg/d, you can take raisins, medjool dates, applesauce, bananas, grapes, pineapple etc. These have some fibers but will allow the blood sugar to rise quickly.
If your blood sugar is less than 55 mg/dL you should use 100% grape juice, honey, maple syrup etc that will raise your blood sugars much faster.

Good Luck

further reading references;
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2991551/
2. https://emedicine.medscape.com/article/122122-clinical
3. https://www.lifeextension.com/Protocols/Metabolic-Health/Hypoglycemia/Page-04
4. https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/diabetes-mellitus-dm-and-disorders-of-blood-sugar-metabolism/hypoglycemia
5. https://www.healthline.com/health/hypoglycemia