Short answer: Low blood sugar (hypoglycemia) is the most common Novolin 70/30 side effect, as with all insulin. The label has no trial table with percentages; it lists reactions without rates: redness, swelling or itching at the injection site, rare severe allergy, low potassium, skin pits or thickening, lumps under the skin, swelling and weight gain. Novolin 70/30 has no boxed warning.
What Novolin 70/30 is approved for: Novolin 70/30 is a premixed human insulin, 70% intermediate-acting NPH and 30% short-acting regular insulin. It is approved to improve blood sugar control in adults and children with diabetes. Its fixed proportions do not allow separate basal and mealtime dose changes (section 1).
Source
NOVOLIN 70/30 (insulin isophane human and insulin human) injectable suspension, for subcutaneous use, prescribing information and Patient Information. Novo Nordisk. DailyMed, version published September 29, 2026. DailyMed setid 508a2763-3cb7-4be5-9e53-544e84cd9b1f
No. The current Novolin 70/30 label has no boxed warning.
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Novolin 70/30.
| Reaction | What the label says |
|---|---|
| Hypoglycemia | The most commonly observed adverse reaction in Novolin 70/30 |
| Injection site reactions | Redness, swelling or itching at the site, usually gone in a few days to a few weeks, sometimes needing the insulin to be stopped |
| Metacresol reactions | Local reactions and general muscle aches have been reported with metacresol, an inactive ingredient |
| Hypersensitivity | Severe, life-threatening whole-body allergy, including anaphylaxis |
| Hypokalemia | Insulin shifts potassium into cells, possibly causing low potassium |
| Lipodystrophy | Lipoatrophy (depression in the skin) or lipohypertrophy (enlargement or thickening of tissue) |
| Localized cutaneous amyloidosis | Lumps at the injection site; injecting into them has raised blood sugar, and a sudden switch to an unaffected site has lowered it |
| Peripheral edema | Sodium retention and swelling, particularly if poor control is improved by more intensive insulin therapy |
| Weight gain | Attributed to the anabolic effects of insulin and less sugar lost in the urine |
| Starting or tightening control | Temporary change in eye focus, worsening diabetic eye disease and acute painful nerve symptoms |
| Medication errors | Other insulins given by mistake in place of Novolin 70/30 |
| Immunogenicity | Anti-insulin antibodies may form; the rate with Novolin 70/30 is unknown |
The label gives no rates and no placebo or comparator column for Novolin 70/30.
The label calls Novolin 70/30 an intermediate-acting insulin with up to 24 hours duration of action. Under the skin, its glucose-lowering effect begins about 30 minutes after the dose, and timing can vary a lot between people and in the same person.
The Patient Information lists the most common side effects as low blood sugar, allergic reactions including reactions at the injection site, skin thickening or pits at the injection site, weight gain, and swelling in the hands or feet.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Who should not use it. Novolin 70/30 is not used during an episode of low blood sugar, or by people who have had allergic reactions to it or any of its inactive ingredients.
Never share a FlexPen or syringe. A FlexPen is never shared, even if the needle is changed, and vial users never share needles or syringes, because of the risk of passing on blood-borne infections.
Changes in insulin regimen. Changing insulin strength, maker, type, injection site or method can cause high or low blood sugar, so changes are made under close medical supervision with more glucose checks. In type 2 diabetes, other diabetes medicines may need adjusting.
Low blood sugar. Hypoglycemia is the most common reaction to all insulins. Severe episodes can cause seizures, unconsciousness or death and can affect driving. Awareness of lows may be reduced with long diabetes, nerve damage, beta-blockers or repeated lows. Kidney or liver problems can raise the risk.
Medication mix-ups. Mix-ups between Novolin 70/30 and other insulins have been reported, so the insulin label is checked before each injection.
Serious allergic reactions. Severe, life-threatening whole-body allergy, including anaphylaxis, can occur, with signs such as whole-body rash, trouble breathing, wheezing, low blood pressure, fast heartbeat or sweating. Novolin 70/30 is stopped if it does.
Low potassium. All insulins shift potassium into cells and can cause low potassium, which untreated can cause breathing paralysis, heart rhythm problems and death.
Heart failure with TZDs. Thiazolidinediones (such as pioglitazone) with insulin can cause dose-related fluid retention that may lead to or worsen heart failure. Stopping or lowering the TZD is considered if heart failure develops.
From the Patient Information that comes with Novolin 70/30:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.